The invention refers to mechanical engineering, namely to fluid pressure actuators and hydraulics, namely to fluid-pressure actuators. On the other hand the invention may also belong to performing operations, in particular to hydraulic control devices for rope or chain winding mechanisms of winches.
The purpose of the invention is to create a hydraulic assembly, which would enable driving and controlling of small hydraulic units, in particular hydraulic cylinders for controlling of brake and clutch of a forestry winch, with means to establish and also to maintain a pre-determined pressure of a hydraulic media within the hydraulic circuit, wherein at the same time the hydraulic loss should be as low as possible and the quantity of said hydraulic media required for regular operation and maintaining the pressure within the assembly should also be as low as possible.
As known to those skilled in the art, hydraulic assemblies are used also for the purposes of controlling and driving in the field of forestry winches. A winding drum is driven by means of the internal combustion engine of the belonging tractor via appropriate shaft and a chain reduction gear, and includes a clutch and a brake, which operate alternatively. When the brake is deactivated, the clutch is activated, which then enables turning and driving of a winding drum, upon which by deactivation of said clutch the brake is automatically activated in order to prevent said drum from any further turning. Controlling of said clutch and brake may commonly also be performed by means of electric or any other control units, which is however not always feasible or is much more complicated, when the winch is used in situ, where relevant energy sources are limited or not available at all. Since appropriate hydraulic assembly may no doubt be surmounted to such winch, the pump of which may easily be driven by means of each disposable tractor engine, such appliances for controlling of clutch and brake have already been realized also in the practical use. Appropriate hydraulic circuit comprises a pump, which charges the hydraulic media via appropriately arranged valves and depending on position and adjustment thereof either towards the brake controlling cylinder or a clutch controlling cylinder, by which the residual hydraulic media is then returned back to reservoir i.e. towards said pump. As known to the applicant, a geared pump has exclusively been used for such purposes. Such assembly may no doubt establish a required pressure of the hydraulic media within the hydraulic circuit, but the pump must be able to ensure a sufficient quantity of the media in a required time for the purposes of supplying each cylinder and in order to enable sufficiently short shifting time of control units of the clutch and brake, so that the pumping capacity must be relatively high. Accordingly, the pump must assure sufficiently high capacity all the time, by which the hydraulic loss due to leakage is relatively high, which then in correlation with high pressure results in heating or even overheating of the hydraulic system, which has essential impact to decreasing of quality of hydraulic media and wearing of sealing members, by which the risk of disturbances or damages during operation is then essentially increased. In addition to that, such assembly is pretty bulky when bearing in mind its overall dimensions, not only due to complex and bulky valves included therein, but also due to huge quantity of the hydraulic media and bulky reservoir for storage thereof. It is also obvious, that a hydraulic assembly containing such quantity of hydraulic fluid is not an environment-friendly one, especially when bearing in mind, that said damages may occur during operation in situ, e.g. in the forest or the like.
Various hydraulic circuits are described also in the patent literature, e.g. in FR 2.116.693, JP 58121306A, JP 60263710, JP63083405A, JP 2004176698 or JP 2004360300A, which belong to various devices and are all very complicated and include numerous components, so that the applicant is of opinion, that none of them solves the previously mentioned technical problem, which is however solved by the proposed invention.
A hydraulic assembly for driving and controlling of small hydraulic units, especially of gearbox clutch is described in DE 30 04 067 A1. Such assembly should comprise a reservoir for hydraulic media, a pump intended for producing a required pressure of hydraulic media, as well as a control unit consisting of at least one control valve and at least one hydraulic cylinder. A hydraulic circuit of the hydraulic assembly should include a piston pump, which is at the one hand connected with said control unit and reservoir via a non-return valve, which allows flowing in a direction away from the pump and not in the opposite direction, and on the other hand either via a switching valve with integrated non-return valve, which allows flowing towards the pump but not also in the opposite direction, in a serial manner into a hydraulic circuit together with a pressure storage tank and the non-return valve, or by exceeding a pre-defined pressure by means of automatically shifting of the switching value into a hydraulic circuit, which includes said pump, a switching valve, a control unit and said non-return valve, which are hydraulically interconnected in a serial manner. Such an assembly should enable generating servomechanism power in a sufficient quantity to control all available controlled units.